the control of gene expression 3.8

Question 1

what is a mutation

Answer 1

an alteration to the DNA base sequence
often arise spontaneously during DNA replication

Question 2

what are deletion and addition mutations

Answer 2

where one or more nucleotides are either inserted or deleted from the DNA sequence

Question 3

what is a substitution mutation

Answer 3

where one nucleotide in the DNA sequence is replaced by another

Question 4

what is a duplication mutation

Answer 4

where one or more nucleotides duplicate and repeat

Question 5

what is an inversion mutation

Answer 5

where a group of nucleotides become separated from the DNA sequence then rejoin in reverse order

Question 6

what is a translocation mutation

Answer 6

where a group of nucleotides become separated from the DNA sequence
then are inserted into the DNA of a different chromosome

Question 7

which mutations are likely to have a significant impact and why

Answer 7

insertion deletion duplication translocation

they produce a frameshift
meaning entire amino acid sequence produced will be different

Question 8

which mutations are less likely to have a significant impact and why

Answer 8

substitution inversion

they only alter one or very few triplets
the amino acids sequence might not be affected
due to nature of the genetic code

Question 9

is a mutation resulting in a change to the amino acid sequence always harmful

Answer 9

no
may be neutral if the resulting change in protein has no effect on the organism

may be beneficial - the basis for evolution and natural selection

Question 10

define a mutagenic agent

Answer 10

factors that increase the rate of gene mutation

Question 11

examples of mutagenic agent

Answer 11

chemical mutagens eg alcohol and benzene
ionising radiation eg UV and X-ray

Question 12

define stem cell

Answer 12

undifferentiated cells that divide indefinitely and turn into other specific cell types

Question 13

what are the three types of stem cell

Answer 13

totipotent
pluripotent
multipotent

Question 14

totipotent

Answer 14

can develop into any cell type
including placenta and embryo

Question 15

pluripotent

Answer 15

can develop into any cell type
excluding placenta and embryo

Question 16

multipotent

Answer 16

can only develop into a few different types of cell

Question 17

what happens to totipotent cells during embryonic development

Answer 17

certain parts of DNA are selectively translated
so that only some of the genes are ‘switched on’
in order to differentiate the cell into a specific type and form the tissues that make up the foetus

Question 18

unique feature of pluripotent cells

Answer 18

they can divide in unlimited numbers
therefore can be used to repair or replace damaged tissue

Question 19

what is a unipotent cell

Answer 19

a cell that can only develop into one type of cell
happens at the end of specialisation when the cell can only propagate its own type

Question 20

example of unipotent cell

Answer 20

cardiomyocytes

Question 21

which type of stem cells are found in embryos

Answer 21

totipotent and pluripotent

Question 22

3 uses of stem cells

Answer 22

medical therapies
drug testing on artificially grown tissues
research

Question 23

how are induced pluripotent stem cells produced

Answer 23

from mature fully specialised cells
cell regains capacity to differentiate
through the use of proteins in particular transcription factors

Question 24

what is a transcription factor

Answer 24

a protein that controls the transcription of genes
so that only certain parts of the DNA are expressed

Question 25

how do transcription factors work

Answer 25

move from the cytoplasm into nucleus bind to promoter region upstream of target gene makes it easier or more difficult for RNA polymerase to bind to gene this increases or decreases rate of transcription

Question 26

how does oestrogen affect transcription

Answer 26

diffuses through cell membrane forms hormone-receptor complex with ER alpha oestrogen receptor in the cytoplasm complex enters the nucleus acts as transcription factor to facilitate binding of RNA polymerase

Question 27

what is meant by epigenetics

Answer 27

a heritable change in gene function without change to the base sequence of DNA

Question 28

how does increased methylation of DNA affect gene transcription

Answer 28

addition of a CH3 group to cytosine bases which are next to guanine prevents transcription factors from binding therefore gene transcription is suppressed

Question 29

how does decreased acetylation of DNA affect gene transcription

Answer 29

positively-charged histones bind to negatively charged DNA decreasing acetylation increases positive charge of histones binding becomes too tight and prevents transcription factors from accessing the DNA therefore gene transcription is suppressed

Question 30

how might epigenetic changes affect humans

Answer 30

they can cause disease either by overactivating a gene's function or by suppressing it

Question 31

2 applications of epigenetics

Answer 31

treatments of various diseases development of ways to reverse epigenetic changes

Question 32

describe the process of RNA interference

Answer 32

RNAi is sequence specific silencing of gene expression therefore can be very precise in silencing certain genes

Question 33

RNA interference pathway

Answer 33

double stranded RNA produced by RNA polymerase dsRNA hydrolysed into siRNA siRNA (double stranded) bind to mRNA that has be transcribed from target genes as their base sequence is complementary each siRNA is attached to a protein complex which is able to breakdown the mRNA mRNA is unable to be translated into proteins

Question 34

characteristics of benign tumours (5)

Answer 34

slow growth defined by a clear boundary due to cell adhesion molecules cells retain function and normal shape don't spread easily easy to treat

Question 35

characteristics of malignant tumours (5)

Answer 35

rapid uncontrollable growth ill-defined boundary cells do not retain function and often die spreads quickly and easily difficult to treat

Question 36

describe the role of tumour-suppressor genes

Answer 36

code for proteins that control cell division stop the cell cycle when damage is detected involved in programming apoptosis

Question 37

what is apoptosis

Answer 37

self destruction of the cell

Question 38

explain how tumour suppressor genes can be involved in developing cancer

Answer 38

a mutation in the gene could code for a non functional protein increased methylation or decreased acetylation could prevent transcription cells will divide uncontrollably resulting in a tumour

Question 39

describe the role of proto-oncogenes

Answer 39

control cell division code for proteins that stimulate cell division

Question 40

explain how proto-oncogenes can be involved in developing cancer

Answer 40

mutation in the gene could turn it into a permanently activated oncogene decreased methylation or increased acetylation can cause excess transcription this results in uncontrolled cell division and formation of a tumour

Question 41

explain how abnormal methylation of genes can cause cancer

Answer 41

hyper-methylation of tumour-suppressor genes or oncogenes can impair their function and cause the cell to divide uncontrollably

Question 42

explain how oestrogen can be involved in developing breast cancer

Answer 42

oestrogen is an activator of RNA polymerase therefore in areas of high oestrogen concentration such as adipose tissue in the breasts cell division can be uncontrolled